1. Field of the Invention
This invention relates to television frame signal synchronizing circuits.
2. Description of the Prior Art
In our copending UK patent application No. 8306606 (U.S. Application Ser. No. 582,627) there is described a television signal processing apparatus comprising a plurality of digital television signal processors connected in series between an analog-to-digital converter which converts an input television signal to digital form, and a digital-to-analog (D/A) converter for converting the digital signal back to analog form. At least one of the signal processors is capable of frame synchronizing the digital television signal in dependence on a frame pulse supplied to that signal processor, and a circuit is associated with the D/A converter for producing the frame pulse and for feeding it back to that signal processor. This circuit also operates to synchronize the frame pulse which it produces relative to a source of system television synchronizing signals so that the frame synchronizing signal processor adjusts the timing of the input digital television signal to the D/A converter to bring the output analog television signal into the required synchronism with the system television synchronizing signals.
The present invention is concerned with a television frame signal synchronizing circuit which is particularly suitable for use as the circuit for producing a frame pulse in an apparatus as outlined above.